“A holoprojector—also known as a holo-projector, holojector, hologram projector, holograph projector,[1]holoproj, and the ‘proj[2]—was a device that could record, transmit and receive hologram images. Traditionally, these images were constructed for the purposes of communication, but some holoprojectors were also designed as tools for entertainment and academic purposes. Most astromech droids were outfitted with holo-projector technology.

Holoprojectors create an organized arrangement of light projected to appear as a 3-D replica of the subject. These Holograms were used for communication, information displays, and entertainment. Most holoprojectors were equipped with sound recorders so that a person could hear the subject talk in perfect sync.” – Source: Wookieepedia: The Star Wars Wiki http://starwars.wikia.com/wiki/Holoprojector